Patent GB-685877-A (GB)
Title: Improvements in or relating to change speed transmission
Inventor: SEYBOLD FREDERICK WILLIAM
IPC: F16D67/00
Filed: 1950-08-23
Abstract: 685,877. Change-speed gear. BORG-WARNER CORPORATION. Aug. 23, 1950, No. 20896/50. Class 80 (ii). Four reduced ratios, direct-drive and reverse are provided by two planetary trains combined with a fluid-coupling which, in one form, Fig. 1, is always fully effective in all ratios and in another, Fig. 2 (not shown), is wholly effective in some ratios, wholly ineffective in others and provides a branched drive in others. The invention resides in the selective positive braking of the train reaction-members. In all cases (except reverse) the reaction brakes are helix-mounted one-way ratchet-toothed members co-operating with a selectively - positioned axially - slidable brake-sleeve 47, which, together with two friction disc clutches A, B engaged by fluid-pressure supplied to their pistons 19 through a fourposition rotary distributer-valve 55, controls ratio selection. In Fig. 1, the impeller 11 and turbine 14 of the fluid-coupling are secured respectively to a rotary casing 12 fast to the input shaft 10, and to a ring-gear 16 of a first sun-ring train, the planet-carrier 29 of which is permanently fast to a large bevel side-wheel 24 of a second train having bevel stepped planets carried by the final output shaft 42, a small bevel side-wheel 23, connected through the friction clutch A to the fluid-coupling turbine 14, and a large reaction side-wheel 36, connected through the friction clutch B to the first planet-carrier 29. One reaction member, the first planet-carrier 29, used as such only in reverse, is held by a twoway toothed brake' 31, 51, but the other two, viz. the large bevel 36 and first sun 32, are selectively held by one-way brakes. These comprise, for the large bevel 36 an inner sleeve 39 (see also Fig. 10) fast to the bevel and having external helical splines 40 engaging complementary splines in a sleeve 41 having at its right end facial ratchet teeth for engagement with a radially inner region of similar, but radially longer teeth 53 on the axially movable non- rotary brake-sleeve 47, splined at 49 in the fixed casing. The sleeve 41 slides freely, with oil-film clearance only, in a surrounding sleeve 33 which is fast to the first reaction sun 32, and also has external splined engagement with a further surrounding sleeve 35 having facial ratchet teeth at its right end, for engagement with a radially outer region of the teeth 53 of the brake-sleeve 47, in which sleeve it has oilfilm clearance only. Rightward axial movement of the two helically-slidable toothed sleeves 41 and 35 is positively limited to different extents by flanges 41a, 35a respectively to co-operate selectively with the toothed outer brake-sleeve 47 as described below. Ratio selection.-The brake-sleeve 47 is axially movable by a control-fork from an extreme rightward position, giving reverse, in which axial teeth 51 on the sleeve engage teeth 31 on the first planet-carrier 29. Moving the brakesleeve 47 one step leftwards frees all the reaction-members for neutral. A second step leftwards provides an emergency low position in which the ratchet brake-teeth 53 of the sleeve 47 engage only the teeth of the inner helixsleeve 41, thus holding the large reaction bevel against backward rotation, oil drag between the various sleeves causing initial engagement by helix advancement of the sleeve 41. Engagement of the friction clutch A, by the selector-valve 55, passes the power through the fluid-coupling and clutch A to the small bevel 23 so that the bevel train acts alone to give an emergency low ratio (5 to 1) to the output carrier. A further and final leftward step of the brake-sleeve 47 into the invariable position, which it occupies for all the remaining four normal forward ratios, causes its ratchet brake-teeth 53 to engage simultaneously both concentric sets of teeth on the helix-sleeves 41, 33, thus holding both the large reaction-bevel 36 and spur sun 32 against reverse rotation. With neither clutch A or B engaged a normal low is obtained by drive through the fluid-coupling to the first ring-gear 16, which drives, at reduced speed through the first planet-carrier 29, the large bevel 24, to cause the smaller bevel planets to roll on the large reaction bevel 36 and, through the planetcarrier, to drive the output shaft 42 at an overall reduced ratio of 3.2 to 1. Engaging the clutch A by the selector-valve 55, whilst maintaining the reduced drive through the ring-gear 16 to the large bevel 24, drives also from the fluid-coupling through the clutch A direct to the small bevel 23 producing a first intermediate ratio of 2 to 1 overall. Frictional oil-drag between the helix-sleeve 41 and the now forwardly rotating large bevel 36 moves the helix-sleeve 41 to the left, out of engagement with the teeth 53 of the brake-sleeve 47. Disengaging the clutch A and engaging B, by the selector-valve 55, clutches the large reaction bevel 36 to the planet-carrier 29, so that the two large bevels 24, 36 now rotate at the same reduced forward speed and the bevel train is locked, giving a second intermediate ratio of 1.6 to 1 overall. Engaging both clutches A and B together, by the selector-valve 55, the large bevels 24, 36 are locked together and the bevel train drives solid from the small side-wheel 23 to the output carrier, giving high speed, 1 to 1 overall. Reverse is by moving the brake-sleeve to the extreme right to mesh the brake-teeth 31, 51, holding the large bevel 24 through the carrier 29; and engaging the clutch A to drive the small bevel 23, thus rotating the output carrier reversely at 3 to 1 ratio. A negative-torque one-way clutch 43, arranged directly between input and output shafts 10, 42, provides engine-brake torque at 1 to 1 under all conditions, and a second oneway clutch 61 between the large reaction bevel 36 and output shaft 42 prevents backward roll of a vehicle when in forward gear on an upgrade. The one-way clutch 61 is ineffective in reverse, since in that ratio the bevel 36 rotates in the same direction as the output shaft and at twice its speed. In Fig. 2 (not shown), the clutch A is arranged forward of the fluid-coupling and directly connecting the input shaft to the small bevel 23. Numerical ratios are unaffected, but in this case, emergency low, high and reverse are wholly mechanical; low and second intermediate wholly fluid; and first intermediate a split-torque hydromechanical drive. Numerical torque valves on all elements in all ratios for each construction are tabulated in the Specification.